The present invention relates to a decoding apparatus which receives and decodes data on a dedicated physical control channel and data on a dedicated physical data channel, which are coded into a complex code of a single system which is transmitted as an uplink signal from a mobile unit to a base station in a 3rd generation cell phone system, a decoding method for the decoding apparatus, and a radio base station apparatus using the decoding apparatus.
A radio base station apparatus in a digital cell phone system such as a CDMA system is required to improve the reception characteristics (decoding characteristics) with respect to the necessary communication quality (SIR: Signal to Interference power Ratio) for each mobile station (user). This is because improving the decoding characteristics can save excessive transmission power control and minimize interference with other users. This has great influences on communication quality and channel capacity. A reception SIR is often measured by using a pilot bit on a dedicated control channel, which is used for closed loop transmission power control, maximum ratio combining in RAKE combining operation in CDMA, and the like.
As a radio base station apparatus in a next-generation (3rd generation) cell phone system, an apparatus is used, which decodes information coded according to TFCI (Transport Format Combination Indicator) written in specifications TS25.212 of 3GPP (3rd Generation Partnership Project) which is a standards institute. Various kinds of decoding techniques for such TFCI codes have been proposed (see, e.g., Japanese Patent Laid-Open No. 2002-26735 (p. 2, FIGS. 6 to 8) and Japanese Patent Laid-Open No. 2001-245359 (pp. 2-3, FIGS. 1 and 2).
Uplink dedicated physical channels (DPCHs) from mobile stations to a base station in a next-generation (3rd generation) cell phone system include a dedicated physical control channel (DPCCH) for transferring various kinds of control information including TFCI information and dedicated physical data channels (DPDCHs) for transferring user data. Data on these channels of a plurality of systems are respectively spread by different spreading codes and then modulated into a complex code (I+jQ) of a signal system to be transmitted to a base station through a radio link.
Therefore, data on a dedicated physical control channel and data on dedicated physical data channels which are decoded by the radio base station apparatus are exposed to the same radio wave environment on a radio link, and hence they are associated with each other in terms of error occurrence.
A code vector generated by coding TFCI information which is written in TS25.212 is basically a row vector of a Walsh matrix, i.e., a quadrature code. For this reason, when a TFCI value is to be decoded, the quadrature correlation characteristics can be used. The conventional TFCI decoding technique is, however, aimed at only decoding operation for obtaining TFCI information on a dedicated physical control channel, but is not designed to perform error data correction processing for a dedicated physical data channel by using the correlation characteristics obtained at that time.